US20030204763A1 - Memory controller and method of aligning write data to a memory device - Google Patents
Memory controller and method of aligning write data to a memory device Download PDFInfo
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- US20030204763A1 US20030204763A1 US10/134,957 US13495702A US2003204763A1 US 20030204763 A1 US20030204763 A1 US 20030204763A1 US 13495702 A US13495702 A US 13495702A US 2003204763 A1 US2003204763 A1 US 2003204763A1
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C7/00—Arrangements for writing information into, or reading information out from, a digital store
- G11C7/10—Input/output [I/O] data interface arrangements, e.g. I/O data control circuits, I/O data buffers
- G11C7/1078—Data input circuits, e.g. write amplifiers, data input buffers, data input registers, data input level conversion circuits
- G11C7/1084—Data input buffers, e.g. comprising level conversion circuits, circuits for adapting load
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
- G11C11/21—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements
- G11C11/34—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements using semiconductor devices
- G11C11/40—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements using semiconductor devices using transistors
- G11C11/401—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements using semiconductor devices using transistors forming cells needing refreshing or charge regeneration, i.e. dynamic cells
- G11C11/4063—Auxiliary circuits, e.g. for addressing, decoding, driving, writing, sensing or timing
- G11C11/407—Auxiliary circuits, e.g. for addressing, decoding, driving, writing, sensing or timing for memory cells of the field-effect type
- G11C11/409—Read-write [R-W] circuits
- G11C11/4093—Input/output [I/O] data interface arrangements, e.g. data buffers
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C7/00—Arrangements for writing information into, or reading information out from, a digital store
- G11C7/10—Input/output [I/O] data interface arrangements, e.g. I/O data control circuits, I/O data buffers
- G11C7/1006—Data managing, e.g. manipulating data before writing or reading out, data bus switches or control circuits therefor
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C7/00—Arrangements for writing information into, or reading information out from, a digital store
- G11C7/10—Input/output [I/O] data interface arrangements, e.g. I/O data control circuits, I/O data buffers
- G11C7/1051—Data output circuits, e.g. read-out amplifiers, data output buffers, data output registers, data output level conversion circuits
- G11C7/1066—Output synchronization
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C7/00—Arrangements for writing information into, or reading information out from, a digital store
- G11C7/10—Input/output [I/O] data interface arrangements, e.g. I/O data control circuits, I/O data buffers
- G11C7/1072—Input/output [I/O] data interface arrangements, e.g. I/O data control circuits, I/O data buffers for memories with random access ports synchronised on clock signal pulse trains, e.g. synchronous memories, self timed memories
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C7/00—Arrangements for writing information into, or reading information out from, a digital store
- G11C7/10—Input/output [I/O] data interface arrangements, e.g. I/O data control circuits, I/O data buffers
- G11C7/1078—Data input circuits, e.g. write amplifiers, data input buffers, data input registers, data input level conversion circuits
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C7/00—Arrangements for writing information into, or reading information out from, a digital store
- G11C7/10—Input/output [I/O] data interface arrangements, e.g. I/O data control circuits, I/O data buffers
- G11C7/1078—Data input circuits, e.g. write amplifiers, data input buffers, data input registers, data input level conversion circuits
- G11C7/1087—Data input latches
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C7/00—Arrangements for writing information into, or reading information out from, a digital store
- G11C7/10—Input/output [I/O] data interface arrangements, e.g. I/O data control circuits, I/O data buffers
- G11C7/1078—Data input circuits, e.g. write amplifiers, data input buffers, data input registers, data input level conversion circuits
- G11C7/1093—Input synchronization
Definitions
- the present invention relates to memory controllers. More particularly, the present invention relates to memory controllers and methods of aligning write data provided to a memory device, where the data is aligned with respect to a data clock strobe signal that is generated from the memory controller.
- DDR double data rate dynamic random access memory
- a memory controller is often used to coordinate the transfer of data to and from a memory device, such as a DDR DRAM.
- the memory controller provides a clock strobe signal to the memory device for synchronizing write operations.
- the memory device uses the clock strobe signal for determining when the write data is valid and can therefore be latched.
- data to a DDR DRAM transitions twice per clock period.
- data to a DDR DRAM transitions with a 1 ⁇ 4 clock phase shift from the data clock strobe as measured at the memory device.
- the memory controller is responsible for creating this phase shift with appropriate timing to insure correct operation of the memory device. In previous controllers, the controller has used a clock signal having two times (2 ⁇ ) the frequency of a system clock signal.
- a current approach to creating the desired phase shift is to invert the 2 ⁇ clock signal, and to use the falling edge of the inverted 2 ⁇ clock as the event that transitions write data to the memory device. This approach can have certain limitations and/or can necessitate added circuit complexity.
- Clock generation circuits such as oscillators or phase locked loops (PLLs), coupled with asymmetries introduced by clock tree routing, do not provide a uniform duty cycle (i.e., the time that the clock signal is observed as being high is different than the time the clock signal is observed as being low).
- a uniform duty cycle is important, a clock of twice the desired frequency (i.e., the 2 ⁇ clock) may be used and divided by two to create a symmetrical clock. In the case of DDR DRAM, this would require the generation and distribution of a 4 ⁇ clock, which is not desirable due to the high frequencies involved.
- a memory controller for aligning write data and a clock strobe signal provided to a memory device includes a delay line coupled to a local clock input and providing as an output a delayed local clock signal.
- a first latch circuit receives data to be written to the memory device as an input and has an output coupled to a data input of the memory device.
- the first latch circuit is clocked by a first one of the local clock signal and the delayed local clock signal and provides in response the write data to the data input of the memory device.
- a clock strobe generating circuit is clocked by a second one of the local clock signal and the delayed local clock signal.
- the clock strobe generating circuit has an output coupled to a clock strobe input of the memory device and provides the clock strobe signal to the memory device.
- the delay, between the local clock signal and the delayed local clock signal, introduced by the delay line aligns transitions in the data provided to the data input of the memory device and transitions in the clock strobe provided to the memory device without the need for inversion of the local clock signal and precise control of the duty cycle of the local clock signal.
- the delay line is a programmable delay line, while in other embodiments the delay line is a fixed (non-programmable) delay line.
- the memory device is a double data rate (DDR) dynamic random access memory (DRAM) device, but the memory controller of the invention can be used to align write data and a clock strobe for other types of memory devices as well.
- DDR double data rate
- DRAM dynamic random access memory
- the memory controller circuit delays the clock strobe with respect to the data, rather than the data with respect to the clock strobe, thereby also creating the desired phase shift.
- FIG. 1 is a schematic diagram of a portion of a memory controller coupled to a memory device according to one embodiment of the present invention.
- FIG. 2 is a schematic diagram of a portion of a memory controller coupled to a memory device according to a second embodiment of the present invention.
- FIG. 1 is a schematic diagram of a memory controller 10 coupled to a memory device 12 according to one embodiment of the present invention.
- Memory controller 10 has an internal local clock signal CLK2 ⁇ , which is used for synchronizing various functions within the memory controller including the capture of data received from memory device 12 and for synchronizing read and write operations within memory device 12 .
- Internal local clock signal CLK2 ⁇ is, in some embodiments, a clock signal having twice the frequency as a system clock signal CLK.
- the 1 ⁇ system clock signal CLK is generated from the 2 ⁇ clock signal CLK2 ⁇ , though the opposite could also be true in some embodiments.
- memory device 12 is a double data rate (DDR) dynamic random access memory (DRAM).
- DDR double data rate
- memory device 12 includes an N bit data input 16 labeled “DQ[7:0]” and a data clock strobe input 18 labeled “DQS”.
- N is equal to 4, 8 or 32 bits, but the invention is not limited to these values of N.
- Memory device 12 receives data DQ[7:0], at input 16 , which needs to be aligned with a data clock strobe DQS received by the memory device at input 18 .
- DQ[7:0] should be aligned such that it transitions in the middle of the stable region of the DQS strobe, though transitions other than in the middle of the stable region of the DQS strobe may also be desirable.
- memory controller 10 includes a delay line 20 and latches 24 , 30 and 32 .
- delay line 20 is a programmable delay line having a plurality of propagation delay settings that are programmable through delay control input 34 .
- delay line 20 has a fixed or non-programmable delay.
- Latches 24 and 30 can be N bit latches for latching N bit data through to provide data DQ[7:0] at input 16 of memory device 12 .
- latches 24 , 30 and 32 include D-type flip-flops which latch data on the rising edges of the clock signals applied to the latches. Other types of latches can be used in other alternative embodiments.
- FIG. 1 illustrates only portions of memory controller 10 which are useful in explaining the concepts of the invention, and components other than those shown can be included in memory controller 10 . Further, the particular components shown in FIG. 1 can be replaced with other components and configurations without departing from the invention. Also, other illustrated components are optional.
- control circuitry 36 can optionally be included in memory controller 10 to provide the delay control input 34 .
- delay control input 34 can be a fixed value programmed into delay line 20 and control circuitry 36 can be omitted. In yet other embodiments, no delay control input is required.
- the clock signal CLK2 ⁇ is used to clock latch 32 to create a symmetrical clock strobe DQS at input 18 to memory device 12 .
- the same clock signal CLK2 ⁇ is used to clock latch 24 in order to latch N bit input data (labeled DQ[7:0]_IN) to N bit output 28 .
- Clock signal CLK2 ⁇ that is used to create the symmetrical DQS is delayed using programmable delay line 20 to create at output 22 a delayed clock CLK2 ⁇ _DEL such that the delay between CLK2 ⁇ and CLK2 ⁇ _DEL is optimized.
- the delay for the system is optimized by setting it to 1 ⁇ 4 of a system clock period (1 ⁇ 2 of a CLK2 ⁇ period).
- Delayed clock signal CLK2 ⁇ _DEL is used to clock latch 30 in order to latch the N bit data 28 to data DQ[7:0] at input 16 of memory device 12 .
- the delay between clock signal CLK2 ⁇ and delayed clock signal CLK2 ⁇ _DEL may be adjusted using delay control input 34 for a more optimal value such that the delay results in DQ[7:0] transitioning in the middle of the stable region of the DQS strobe at memory device 12 , rather than at the signal's origin within the memory controller.
- the delay line may need to be calibrated or alternatively used with a master digital locked loop (DLL) that would allow the delay to be scaled with respect to a fixed clock period.
- the DLL can be considered to be part of control circuitry 36 .
- the present invention includes a memory controller 10 for aligning write data DQ[7:0] and a clock strobe signal DQS provided to a memory device 12 .
- the memory controller includes a local clock input 15 providing a local clock signal CLK2 ⁇ .
- the memory controller also includes a delay line 20 coupled to the local clock input and providing as an output a delayed local clock signal CLK2 ⁇ _DEL.
- a first latch circuit 30 receives data to be written to the memory device as an input and has an output coupled to the data input 16 of the memory device.
- the first latch circuit is clocked by a first one of the local clock signal CLK2 ⁇ and the delayed local clock signal CLK2 ⁇ _DEL and provides in response the write data DQ[ 7 : 0 ] to the data input of the memory device.
- first latch circuit 30 is clocked using the delayed local clock signal CLK2 ⁇ _X-DEL, but the opposite could be true in other embodiments.
- a clock strobe generating circuit 32 is clocked by the second (or other) one of the local clock signal and the delayed local clock signal. In the illustrated embodiment, circuit 32 is clocked using local clock signal CLK2 ⁇ , but again the opposite could be true.
- the clock strobe generating circuit 32 has an output coupled to a clock strobe input 18 of the memory device 12 and provides the clock strobe signal to the memory device.
- FIG. 2 is a schematic diagram of a second embodiment of the memory controllers of the present invention as discussed above.
- Memory controller 200 can include components which are substantially identical to those shown in memory controller 10 of FIG. 1.
- components of memory controller 200 are labeled with reference numbers which correspond in their last two digits to reference numbers of corresponding components in FIG. 1.
- a primary difference between memory controller 200 and memory controller 10 is that, in memory controller 200 , input data DQ[7:0]_IN is provided to latch 232 (corresponding to latch 32 in FIG. 1), instead of to latch 224 (corresponding to latch 24 in FIG. 1).
- latch 232 can serve as the first latch circuit
- latches 224 and/or 230 can serve as the clock strobe generating circuit.
- data input 216 of memory device 212 which receives data DQ[7:0] is coupled to latch 232 in this embodiment.
- data clock strobe input 218 which receives clock strobe DQS, is coupled to the output of latch 230 .
- the delay line 220 is used to delay clock strobe DQS with respect to data DQ[7:0], rather than the data with respect to the clock strobe, thereby also creating the desired phase shift.
- the memory controller can be used with any memory device (or register) where the write data is aligned with respect to a clock strobe that originates from the memory controller.
- the invention is not limited to the particular arrangement of latches shown in FIG. 1. More generally, the invention is directed to memory controllers in which a clock strobe provided to the memory device must be aligned with the write data to be stored.
- the term “coupled” used in the specification and the claims can include a direct connection and a connection through one or more intermediate components.
Abstract
Description
- The present invention relates to memory controllers. More particularly, the present invention relates to memory controllers and methods of aligning write data provided to a memory device, where the data is aligned with respect to a data clock strobe signal that is generated from the memory controller.
- Certain types of memory devices require a clock strobe signal having edges that are aligned with the center of changes in the write data. A double data rate (DDR) dynamic random access memory (DRAM) registers data on each rising and falling edge of the clock strobe signal. A DDR DRAM therefore accepts or registers two data words per clock cycle.
- A memory controller is often used to coordinate the transfer of data to and from a memory device, such as a DDR DRAM. The memory controller provides a clock strobe signal to the memory device for synchronizing write operations. The memory device uses the clock strobe signal for determining when the write data is valid and can therefore be latched. As mentioned, data to a DDR DRAM transitions twice per clock period. Ideally, data to a DDR DRAM transitions with a ¼ clock phase shift from the data clock strobe as measured at the memory device. The memory controller is responsible for creating this phase shift with appropriate timing to insure correct operation of the memory device. In previous controllers, the controller has used a clock signal having two times (2×) the frequency of a system clock signal. A current approach to creating the desired phase shift is to invert the 2× clock signal, and to use the falling edge of the inverted 2× clock as the event that transitions write data to the memory device. This approach can have certain limitations and/or can necessitate added circuit complexity.
- Clock generation circuits, such as oscillators or phase locked loops (PLLs), coupled with asymmetries introduced by clock tree routing, do not provide a uniform duty cycle (i.e., the time that the clock signal is observed as being high is different than the time the clock signal is observed as being low). When a uniform duty cycle is important, a clock of twice the desired frequency (i.e., the 2× clock) may be used and divided by two to create a symmetrical clock. In the case of DDR DRAM, this would require the generation and distribution of a 4× clock, which is not desirable due to the high frequencies involved. If an asymmetrical duty cycle 2× clock is used to align the write data, the operational frequency of the memory can be limited and the resulting system will have less margin surrounding timing of write data with respect to the data clock strobes. Improved memory controller circuits are therefore desired that are capable of aligning write data provided to a memory device, with respect to a data clock strobe signal that is generated from the memory controller, without one or more of the aforementioned limitations or requirements.
- A memory controller for aligning write data and a clock strobe signal provided to a memory device includes a delay line coupled to a local clock input and providing as an output a delayed local clock signal. A first latch circuit receives data to be written to the memory device as an input and has an output coupled to a data input of the memory device. The first latch circuit is clocked by a first one of the local clock signal and the delayed local clock signal and provides in response the write data to the data input of the memory device. A clock strobe generating circuit is clocked by a second one of the local clock signal and the delayed local clock signal. The clock strobe generating circuit has an output coupled to a clock strobe input of the memory device and provides the clock strobe signal to the memory device. The delay, between the local clock signal and the delayed local clock signal, introduced by the delay line aligns transitions in the data provided to the data input of the memory device and transitions in the clock strobe provided to the memory device without the need for inversion of the local clock signal and precise control of the duty cycle of the local clock signal.
- In some embodiments of the invention, the delay line is a programmable delay line, while in other embodiments the delay line is a fixed (non-programmable) delay line.
- In some embodiments of the present invention, the memory device is a double data rate (DDR) dynamic random access memory (DRAM) device, but the memory controller of the invention can be used to align write data and a clock strobe for other types of memory devices as well.
- In some embodiments of the present invention, the memory controller circuit delays the clock strobe with respect to the data, rather than the data with respect to the clock strobe, thereby also creating the desired phase shift.
- FIG. 1 is a schematic diagram of a portion of a memory controller coupled to a memory device according to one embodiment of the present invention.
- FIG. 2 is a schematic diagram of a portion of a memory controller coupled to a memory device according to a second embodiment of the present invention.
- FIG. 1 is a schematic diagram of a
memory controller 10 coupled to amemory device 12 according to one embodiment of the present invention.Memory controller 10 has an internal local clock signal CLK2×, which is used for synchronizing various functions within the memory controller including the capture of data received frommemory device 12 and for synchronizing read and write operations withinmemory device 12. Internal local clock signal CLK2× is, in some embodiments, a clock signal having twice the frequency as a system clock signal CLK. Typically, the 1× system clock signal CLK is generated from the 2× clock signal CLK2×, though the opposite could also be true in some embodiments. - In some embodiments of the invention,
memory device 12 is a double data rate (DDR) dynamic random access memory (DRAM). In the example shown in FIG. 1,memory device 12 includes an Nbit data input 16 labeled “DQ[7:0]” and a dataclock strobe input 18 labeled “DQS”. Using typical DDR DRAM memory devices, N is equal to 4, 8 or 32 bits, but the invention is not limited to these values ofN. Memory device 12 receives data DQ[7:0], atinput 16, which needs to be aligned with a data clock strobe DQS received by the memory device atinput 18. For the maximum amount of margin in a system and the highest operating frequency, DQ[7:0] should be aligned such that it transitions in the middle of the stable region of the DQS strobe, though transitions other than in the middle of the stable region of the DQS strobe may also be desirable. - In the embodiment illustrated in FIG. 1,
memory controller 10 includes a delay line 20 andlatches delay control input 34. However, in other embodiments, delay line 20 has a fixed or non-programmable delay.Latches input 16 ofmemory device 12. In one embodiment,latches - FIG. 1 illustrates only portions of
memory controller 10 which are useful in explaining the concepts of the invention, and components other than those shown can be included inmemory controller 10. Further, the particular components shown in FIG. 1 can be replaced with other components and configurations without departing from the invention. Also, other illustrated components are optional. For example,control circuitry 36 can optionally be included inmemory controller 10 to provide thedelay control input 34. However, in other embodiments,delay control input 34 can be a fixed value programmed into delay line 20 andcontrol circuitry 36 can be omitted. In yet other embodiments, no delay control input is required. - The clock signal CLK2× is used to clock
latch 32 to create a symmetrical clock strobe DQS atinput 18 tomemory device 12. The same clock signal CLK2× is used to clocklatch 24 in order to latch N bit input data (labeled DQ[7:0]_IN) toN bit output 28. Clock signal CLK2× that is used to create the symmetrical DQS is delayed using programmable delay line 20 to create at output 22 a delayed clock CLK2×_DEL such that the delay between CLK2× and CLK2×_DEL is optimized. In some embodiments, the delay for the system is optimized by setting it to ¼ of a system clock period (½ of a CLK2× period). Though in typical cases the delay setting will be ¼ of the system clock period, it is not a requirement of the invention that the delay be set to 1/4 of the system clock period. In fact, in can be advantageous to factor the optimal setup and hold time into this delay setting, as well as factoring in clock rise/fall asymmetries. Delayed clock signal CLK2×_DEL is used to clocklatch 30 in order to latch theN bit data 28 to data DQ[7:0] atinput 16 ofmemory device 12. - The delay between clock signal CLK2× and delayed clock signal CLK2×_DEL may be adjusted using
delay control input 34 for a more optimal value such that the delay results in DQ[7:0] transitioning in the middle of the stable region of the DQS strobe atmemory device 12, rather than at the signal's origin within the memory controller. In order to accurately set the delay line to a fixed percentage of a clock period, the delay line may need to be calibrated or alternatively used with a master digital locked loop (DLL) that would allow the delay to be scaled with respect to a fixed clock period. In such embodiments, the DLL can be considered to be part ofcontrol circuitry 36. - In the conventional approach which is not utilized in
memory controller 10 of the present invention, alignment of clock strobe DQS with data DQ[7:0] would be accomplished by inverting clock signal CLK2× and using this inverted clock signal to latch the write data to the memory device. Then, the rising edge of this inverted clock signal would be used to register the data. This can require more precise control over the duty cycle of clock signal CLK2×. Using delay line 20 to align data DQ[7:0] with clock strobe signal DQS minimizes the necessity to maintain precise control over this duty cycle. Use of delay line 20 in this manner does not require the use of both edges of the clock signal, relying solely on the rising edge. - In summary, the present invention includes a
memory controller 10 for aligning write data DQ[7:0] and a clock strobe signal DQS provided to amemory device 12. The memory controller includes alocal clock input 15 providing a local clock signal CLK2×. The memory controller also includes a delay line 20 coupled to the local clock input and providing as an output a delayed local clock signal CLK2×_DEL. Afirst latch circuit 30 receives data to be written to the memory device as an input and has an output coupled to thedata input 16 of the memory device. The first latch circuit is clocked by a first one of the local clock signal CLK2× and the delayed local clock signal CLK2×_DEL and provides in response the write data DQ[7:0] to the data input of the memory device. In the illustrated embodiment,first latch circuit 30 is clocked using the delayed local clock signal CLK2×_X-DEL, but the opposite could be true in other embodiments. A clockstrobe generating circuit 32 is clocked by the second (or other) one of the local clock signal and the delayed local clock signal. In the illustrated embodiment,circuit 32 is clocked using local clock signal CLK2×, but again the opposite could be true. The clockstrobe generating circuit 32 has an output coupled to aclock strobe input 18 of thememory device 12 and provides the clock strobe signal to the memory device. - FIG. 2 is a schematic diagram of a second embodiment of the memory controllers of the present invention as discussed above.
Memory controller 200 can include components which are substantially identical to those shown inmemory controller 10 of FIG. 1. In FIG. 2, components ofmemory controller 200 are labeled with reference numbers which correspond in their last two digits to reference numbers of corresponding components in FIG. 1. A primary difference betweenmemory controller 200 andmemory controller 10 is that, inmemory controller 200, input data DQ[7:0]_IN is provided to latch 232 (corresponding to latch 32 in FIG. 1), instead of to latch 224 (corresponding to latch 24 in FIG. 1). Thus, in this embodiment, latch 232 can serve as the first latch circuit, whilelatches 224 and/or 230 can serve as the clock strobe generating circuit. Note that the data input 216 of memory device 212, which receives data DQ[7:0], is coupled to latch 232 in this embodiment. Likewise, dataclock strobe input 218, which receives clock strobe DQS, is coupled to the output oflatch 230. As a result, the delay line 220 is used to delay clock strobe DQS with respect to data DQ[7:0], rather than the data with respect to the clock strobe, thereby also creating the desired phase shift. - Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. For example, the memory controller can be used with any memory device (or register) where the write data is aligned with respect to a clock strobe that originates from the memory controller. Further, the invention is not limited to the particular arrangement of latches shown in FIG. 1. More generally, the invention is directed to memory controllers in which a clock strobe provided to the memory device must be aligned with the write data to be stored. In addition, the term “coupled” used in the specification and the claims can include a direct connection and a connection through one or more intermediate components.
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US5764591A (en) * | 1996-04-04 | 1998-06-09 | Fujitsu Limited | Memory device and memory control circuit |
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Cited By (11)
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US7486702B1 (en) * | 2003-08-11 | 2009-02-03 | Cisco Technology, Inc | DDR interface for reducing SSO/SSI noise |
JP2005141725A (en) * | 2003-10-16 | 2005-06-02 | Pioneer Plasma Display Corp | Memory access circuit, operating method therefor, and display device using the memory access circuit |
WO2008024659A2 (en) * | 2006-08-22 | 2008-02-28 | Atmel Corporation | Circuits to delay a signal from a memory device |
WO2008024659A3 (en) * | 2006-08-22 | 2008-06-26 | Atmel Corp | Circuits to delay a signal from a memory device |
US20090033391A1 (en) * | 2006-08-22 | 2009-02-05 | Atmel Corporation | Circuits to delay a signal from a memory device |
US20090238016A1 (en) * | 2006-08-22 | 2009-09-24 | Atmel Corporation | Circuits to delay signals from a memory device |
US7701802B2 (en) * | 2006-08-22 | 2010-04-20 | Atmel Corporation | Circuits to delay a signal from a memory device |
US20090292940A1 (en) * | 2008-05-21 | 2009-11-26 | Nec Electronics Corporation | Memory controller, system including the controller, and memory delay amount control method |
US8201013B2 (en) * | 2008-05-21 | 2012-06-12 | Renesas Electronics Corporation | Memory controller, system including the controller, and memory delay amount control method |
US8359490B2 (en) | 2008-05-21 | 2013-01-22 | Renesas Electronics Corporation | Memory controller, system including the controller, and memory delay amount control method |
US11657846B1 (en) * | 2022-03-31 | 2023-05-23 | Stmicroelectronics S.R.L. | Automatic skew calibration circuit for pattern-dependent dynamic wave shaping for HDD preamplifier write |
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